Rev's restricted to 3500? Power loss.

[Badger]

Hi all, I experienced a strange fault with my Atom 3.5SC this afternoon. For one reason or another my revs were restricted to 3500 pedal flat to the floor. If I hold the pedal position the car doesn't like this and judders/mis-fires slightly and the supercharger seems to stutter.

The Atom is 100% factory standard and no mods to ECU/exhaust etc. etc. and used as intended. Warmed up correctly and cooled down correctly.

Before I get stuck in on any suggestions, I have checked that the oil level is good and quality clean, and the exhaust sensor is clean and in-tact as I removed this as soon as it was cool enough to touch so I could inspect it for carbon etc.

I can't see any loose harness connections, and the car is otherwise faultless. It was serviced around 150 miles previously by Ariel and the total mileage is around 800 only.

I intend to pull the plugs to see what they look like, and inspect wiring for heat damage near to the exhaust.

I'm also going to remove exhaust system to see if the cat innerds have shat out (as it's easy enough to check for an exhaust restriction).

NB Does anyone have a 'special' suggestion on getting a chunky pair of manly-sized hands to the ridiculously placed OBD port on the fire-wall please?

Thanks in advance for anyone who has a remedy.

[John Scherrer]

Really need to be able to see if the ECU is posting any error codes - typically it might be a faulty crank sensor.

Have you tried disconnecting the car battery for an hour and then reconnecting it?
It should/might reset the ECU and sort the issue.

If it's been on track in this recent hot weather without a slow down lap at the end, the wiring behind the exhaust might be fried.

Presumably, it does respond to the throttle pedal, just rev limited at 3,500.

Hope you get it sorted.

[Sir Nick]

I seem to recall that the ECU limits revs if its not getting a speed sensor reading

[Badger]

Thanks for the replies I appreciate it.

I've removed the plugs and checked these (gap and condition is correct/clean).
I've removed lambda sensor and cleaned the soot off it and condition seems fine.
'Checked all wiring in proximity to heat and have continuity along the harness with no evidence of fatigue or melt.
I also lost some skin from my knuckles getting to the obd port but was pleased to see there were no faults stored/logged. what a pain that is unless you have hands the size of a three year old.

After checking the above I noticed from cold and with progressive acceleration the car runs okay, but at full throttle it stutters so I then expected to (possibly) find a restriction with air in/exhaust gases out. I removed the catalyst and it's totally shot so I guess I must have put too much heat through it yesterday in my excitement (2-3 warm up laps and cool-downs for both car and tyres has been my mantra for years and works for me). Maybe I should've put less laps in for each session, who knows (I'm not the cars first owner).

I suppose the 'downside' is I'll have to fit a decat now. Oh no :-D

[Sir Nick]

Well at least you found something solid.

[John Scherrer]

Good find !

Considering the state of the CAT, I suspect 'solid' wasn't the best description Nick

[JT1020]

Good find! Does anyone know if you or have to map the car if you are changing to/from cat to decat pipe? Or vice versa…

Thanks

[speedmachine]

Good find! Does anyone know if you or have to map the car if you are changing to/from cat to decat pipe? Or vice versa…

Thanks

No on the pre 4 cars its not, just fit and forget

[JT1020]

. Thanks for the confirmation

[Badger]

To conclude:
The car has ran faultlessly since fitting the straight-pipe.
Impossible to say if there has been any increase in power/throttle response and so on, and I find it unlikey anyone would notice a decat is now fitted unless they were competing against the clock continuously and shaving 10ths of seconds away. After one day out in the car it's now the same colour as the rest of the exhaust system.
No remap required at all, no faults stored or pending (via obd port diagnostics).

[John Scherrer]

Don’t forget you will need to refit one for the MOT !

[Mrlizard]

there was a forum cat for the 3.5/3 right? is that still about?

[John Scherrer]

There was a Club members CAT last seen with Alex BS back in 2019. Bod was asking where it was in 2021 - don’t know if he found it.

Alex may have handed it over to one of the committee members as he sold his car.

[Sir Nick]

I don't think we three have it...I'll message Bod and ask him.

[Sir Nick]

Yes Bod has it.